The term epitaxy in general describes an ordered crystalline growth of deposited layers. Epitaxial growth of a semiconductor layer has traditionally been achieved by growing a semiconductor material on top of a single crystal substrate, where the crystal lattice of the single crystal substrate matches the crystal lattice of the deposited semiconductor material. Epitaxial layers may be grown with vapor-phase epitaxy (VPE), a modification of chemical vapor deposition (CVD), liquid-phase epitaxy (LPE), and physical vapor deposition (PVD) (evaporative deposition, electron beam physical vapor deposition, sputter deposition, pulse laser deposition, chatodic-arc deposition, and ion beam physical vapor deposition). If a layer is deposited on a substrate of the same composition, the process is called homoepitaxy; otherwise it is called heteroepitaxy. Epitaxy is used in silicon-based manufacturing processes for bipolar junction transistors (BJTs) and modern complementary metal-oxide-semiconductor (CMOS). Epitaxy is also used in production of laser emitting diodes (LEDs) and in solar cells.